I am entitled to some support at least up to the point at which you tell me that you will not provide it. At that point I am not entitled to any support whatever, and it would be rude for me to ask again.
Most CPAN modules are maintained by developers who do provide support. It is reasonable to expect —unless a developer says up front that he will not be providing any support— that he will be providing it.
Not answering legitimate e-mail is not really polite. If a developer is not going to support his product then he ought not to give the impression that he will support it by providing his email address.